Meet the Bates Family - All 20 of Them

Think of the Brady Bunch on steroids, and you might be imagining the 20-person Bates Family.

Gil and Kelly Bates live with their 18 children in a five-bedroom, 4,000-square-foot home in rural Tennessee. At 22, Zach is the oldest child.

"Every year, you know, there was - just add another person - it doesn't feel abnormal to me," Zach said.

The youngest child, Judson, is only four months old.

When asked to name her children, Kelly said, "Oh, Daddy's good at that. His memory's better than mine." Gil Bates easily rattled off all 18 names.

Gil and Kelly Bates, who are evangelical, conservative Christians, didn't really want a big family when they got married 23 years ago. In fact, Gil Bates didn't really like children and Kelly Bates was more concerned with her career than having a big family. But they don't believe in birth control.

Watch the full story on "Nightline" tonight at 11:35 p.m. ET

"We both came to the conclusion that we just wanted to trust God with how many children we had. But we never really thought we'd have 18. We thought maybe one or two, maybe 3," said Gil Bates.

Kelly Bates has been pregnant for most of her adult life.

"It feels more normal for me to be pregnant than not pregnant. I am happy holding a baby. And I'm happy that the children, our lives are so - I talk to so many parents who - their children are lonely. They don't have friends," said Kelly Bates.

In the Bates' case, loneliness is not a problem.

Even with 18 children, Gil and Kelly Bates insist they have time to devote to each child, and for each other.

"Actually now, we probably have more time together than we ever had, even when we just had one or two. Because we'll come home and they'll say, 'Dad, are you taking Mom out?'" said Gil Bates.

The Bates say that the more children they have, the more they can minister to others. They held a Bible study and concert at a nearby nursing home, and used a bus to transport their family to the event.

"So we traveled in a 15-passenger van and a seven-passenger van, we put half in each car. And then we just recently got the bus, so we're looking forward to being all in one car again," said Gil Bates.

Watch the full story or interview on "Nightline" tonight at 11:35 ET

Better Together

The Bates family does almost everything together, from family Bible study to brushing their teeth before bed to family meals around their massive dining room table.

The Bates' laundry room is similar to a dry cleaning business. There are five washing machines and four dryers. Sorting socks for 20 people is a family affair.

"We do laundry at breakfast, lunch and supper," said Kelly Bates. "It only takes ten seconds for this room to become a tornado!"

Doing laundry is not the family's only challenge. Cooking, cleaning the house, doing the dishes, and getting the younger children ready for the day are not easy tasks, and everyone has to pitch in.

Gil Bates runs a tree service and is not wealthy. So how do they afford to feed all their children?

"Honestly, God just directed our steps into tree work. Tree work you can make money with less time and turned out to be a blessing," said Gil Bates.

Eighteen-year-old Lawson is in charge of food shopping. He says he goes to Walmart almost every other day. The bill for one trip is more than $250.

Kelly home schools her children. She teaches classes for the younger ones, and the older children study on the computer.

"As our family increased, technology has, and we have school on video, we have science and history on video, we have it on computer now. So, a lot of my work is done for me, which is a real blessing," said Kelly Bates.

When asked if she thinks her children get a good education, Kelly Bates replied, "Yes, I do. In fact, Zach, Michael and Erin have been full-time students in college and all three of them ended this past semester with 4.0s."

Even the college-age children live at home. This bedroom sleeps eight of the ten sisters, from age 20 down to 16-month-old Callie.

"They like it that way. We gave them the choice when we were designing it. We thought, now is your chance," said Kelly Bates. "Cause they'd all been squeezed together for so long, we said now is your chance. You can have your own space if you want it. And they all just unanimously…"

"Almost cried and said, 'Please don't make us go in different rooms,'" added Gil Bates.

"Please don't make us separate! We want to be together," said Kelly Bates.

When asked if they have any privacy, one girl responded, "Well, we do have privacy if we want it, but for the most part, it's like our way of life so we don't mind all of the loud noise."

The house is equipped with an intercom and camera system to keep track of where everyone is.

"I can look and see what's going on in the living room, in the front yard, on the side of the house. When I'm up here, I can tell if kids are sneaking cookies or getting into trouble," said Kelly Bates.

But this high-tech house has no televisions and the computers are only for studying. Instead of watching TV, texting or surfing the internet, the children spend a lot of time practicing musical instruments. They are all musically talented and most of them play more than one instrument, from piano to guitar to violin.

When asked if they felt they were too sheltered, one boy replied, "We do so much stuff. I think we do more than some other people."

Another boy said, "We probably have more opportunities to get out than most."

Kelly is 44, but she hopes to have two more boys for a total of 10 boys and 10 girls.